A 22-year-old woman recently diagnosed with granulomatosis with polyangiitis (GPA) was admitted to the department of cardiology due to chest pain and shortness of breath. The ECG showed widespread mild PR-segment depression, upwardly convex ST-segment elevation, and T-wave inversion. The troponin T level was elevated at 550 ng/L. Transthoracic echocardiography showed basal inferoseptal thinning and hypokinesis, mild pericardial effusion, and an overall preserved left ventricular ejection fraction of 55%. Global longitudinal strain, however, was clearly reduced. Cardiac magnetic resonance imaging (MRI) showed findings consistent with myocarditis but the etiology of the apical hypokinesis could not be determined with certainty and may well have been due to a myocardial infarction, a notion supported by a coronary angiogram displaying slow flow in the territory of the left anterior descending artery. Finally, an endomyocardial biopsy confirmed the diagnosis of myocarditis. The cardiac symptoms subsided upon treatment with high-dose prednisolone and rituximab.